iphone - 绘制两个CGMutablePath Ref的问题

Question

因此，我似乎无法绘制2 CGMutablePathRef。这是代码:

CGRect mainRect = CGRectMake(2, 2, rect.size.width-4, 210);
    CGMutablePathRef mainPathRef = createRoundedRectForRect(mainRect, 4);

    if (self.imageExists_){

        [[UIColor colorWithRed:0 green:0 blue:0 alpha:1.0] set];

        CGContextAddPath(context, mainPathRef);
        CGContextClip(context);
        UIGraphicsBeginImageContext(mainRect.size);

        //need to flip the images to that it is drawn appropriately as CALayer uses a different coordinate system
        CGContextSaveGState(context);
        CGContextTranslateCTM(context, 0.0, 210);
        CGContextScaleCTM(context, 1.0, -1.0);
        CGContextDrawImage(context, mainRect, self.highlightItem_.highlightStoryImage.CGImage);

        UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        [scaledImage drawAtPoint:CGPointMake(0, 0)];
        CGContextRestoreGState(context);

这样就可以在我指定的路径(剪切后)上绘制图像。但是然后我想在其下绘制另一个圆角矩形，所以我这样做了:

 [[UIColor colorWithRed:0 green:0 blue:0 alpha:1.0] set];

     CGFloat colors [] = {
     0.20, 0.20, 0.20, 1.0,
     0.17, 0.17, 0.17, 1.0
     };

     CGColorSpaceRef baseSpace = CGColorSpaceCreateDeviceRGB();
     CGGradientRef gradient = CGGradientCreateWithColorComponents(baseSpace, colors, NULL, 2);
     CGColorSpaceRelease(baseSpace), baseSpace = NULL;

     CGContextSaveGState(context);

     CGRect commentRect = CGRectMake(2, 215, rect.size.width-4, rect.size.height - 215);
     CGMutablePathRef pathRef = createRoundedRectForRect(commentRect, 3);

     CGContextAddPath(context, pathRef);
     CGContextClip(context);

     CGPoint startPoint = CGPointMake(CGRectGetMidX(commentRect), CGRectGetMinY(commentRect));
     CGPoint endPoint = CGPointMake(CGRectGetMidX(commentRect), CGRectGetMaxY(commentRect));

     CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, 0);
     CGGradientRelease(gradient), gradient = NULL;

     CGContextRestoreGState(context);

     CGContextAddPath(context, pathRef);
     CGContextDrawPath(context, kCGPathStroke);

知道为什么这行不通吗？

Answer 1

您已将图形剪切到第一个矩形，但是在第二次绘制之前尚未重置剪切路径。我相信，在调用第一个剪切路径之前，您需要保存图形状态。

您的第一个代码段应如下所示:

CGContextSaveGState(...);
CGContextAddPath(...);
CGContextClip(...);
UIGraphicsBeginImageContext(...);
... rest of your drawing code...
CGContextRestoreGState(...);

然后是第二个代码段。